The parent firm of Japanese advertising giant Dentsu has released the results of an inquiry into a bid-rigging scandal for the Tokyo Olympics and Paralympics.

A report released on Friday says the wrongdoing may have been caused by a corporate culture that places excessive weight on meeting clients' wishes.

Six companies and seven individuals have been indicted for allegedly pre-arranging the winners of tenders to plan and stage test events.

A former Dentsu executive and Dentsu Group itself are among those charged with violating the anti-monopoly law.

Dentsu Group asked third-party experts to conduct the probe.

The results say management was insensitive to legal risks, and blatantly disregarded fairness and transparency.

The report urges Dentsu executives to reform the company's principles and code of conduct.

Dentsu Group launched a panel last month to prevent a similar occurrence.

President Igarashi Hiroshi has acknowledged the company ignored due process.